This invention relates generally to the treatment of diseased or traumatized intervertebral discs, and more particularly, to the use of engineered disc tissues in conjunction with such treatment.
Intervertebral discs provide mobility and a cushion between the vertebrae. At the center of the disc is the nucleus pulposus. The nucleus pulposus is surrounded by the annulus fibrosis, which is comprised of cells (fibrocyte-like and chondrocyte-like), collagen fibers, and non-fibrillar extracellular matrix. The components of the annulus are arranged in 15-25 lamellae around the nucleus pulposus. The fibers in the lamellae alternate their direction of orientation by 30 degrees between each band.
The annulus fibrosis has three important functions. First, the annulus contains the nucleus pulposus. Second, the annulus fibrosis, with other ligaments, connects the vertebrae of the spine. Lastly, the annulus fibrosis helps to control movement between the vertebrae.
The fibers of the annulus can tear causing pain and possible extrusion of the nucleus pulposus. Extrusion of the nucleus pulposus is known as a disc herniation. Disc herniations can compress nerves or the spinal cord resulting in arm or leg pain and dysfunction. Surgery to repair disc herniations leaves a hole in the annulus fibrosis. The hole in the annulus acts as a pathway for additional material to protrude into a nerve, resulting in a recurrence of the herniation.
To date, the treatment of tears or defects of the annulus fibrosis has relied for the most part on eliminating the defective disc or disc function. This may be accomplished by fusing the vertebra on either side of the disc. In terms of replacement, prior-art techniques replace either the nucleus or the nucleus and annulus functions. My co-pending U.S. patent application Ser. No. 09/322,516, and Patent Cooperation Treaty Application Ser. No. PCT/US/14708 describe methods and devices to occlude annular defects.
Certain of my co-pending patent applications and issued patents referenced above recognize that the annulus fibrosis augmentation and/or transplantation techniques described therein are not limited to treatment of the intervertebral disc, and that such techniques may be used to treat other tissues of the body such as the meniscus of the knee. These previous disclosures teach that a meniscus may be removed from recently deceased humans and processed to kill the cells but preserve the extracellular matrix. Fibroctyes or chondrocytes are harvested and added to the meniscus extracellular matrix, as described in my pending U.S. patent application Ser. Nos. 09/639,309, 09/628,727, 09/638,726, and 09/638,242, all of which are incorporated herein by reference.
According to this invention, the transplanted meniscus is used to treat degenerative disc disease, disc herniation, or other pathologic conditions of the spine. Since the meniscus of the knee is capable of handling the high compression and shear loads placed on the meniscus by the bones of the knee, the mechanical properties of the meniscus make it an ideal tissue to transplant to other areas of the body, including the intervertebral disc.
In this embodiment, the harvested fibrocytes are added to a meniscus removed from a suitable donor, preferably a recently deceased human. The harvested meniscus could be processed to kill the cells but preserve the extracellular matrix. Killing the cells of the allograft meniscus minimizes the risk of disease transmission and graft refection. Fibrocytes or chondrocytes would be added to the harvested meniscus extracellular matrix prior to insertion of the engineered meniscus into a patient""s spine. Alternatively, the cells could be added to the harvested meniscus during or after the meniscus is placed into a patient""s spine.
Cells from the meniscus could be also be harvested from a patient""s knee preferably using arthroscopic surgery or other minimally invasive procedure. For example, pieces of damaged meniscus removed by an arthroscopy, could be treated to harvest the cells of the meniscus. The cultured cells from a patient""s meniscus are implanted into the allograft meniscus. The engineered meniscus is surgically implanted into a patient""s spine at a second surgery.
Alternatively, allograft menisci could be transplanted to a patient""s intervertebral disc without adding fibrocytes. In this second embodiment, one relies on the allograft donor cells that remain alive after tissue processing and the ingrowth of the patient""s tissues and cells into the allograft meniscus.
One or more allograft menisci could be placed into the intervertebral disc. The menisci could be sewn or otherwise attached to the patient""s annulus fibrosis. The allograft menisci could be prepared with sutures attached to the menisci to aid the surgeon in surgery. Alternatively, allograft menisci could be morselized and injected into a patient""s disc. The morselized menisci could also be added to a bag like annular augmentation device described in my co-pending U.S. patent application Ser. No. 09/690,536, incorporated herein by reference in its entirety.